1. Field of the Invention
The present invention relates to a method of processing silver halide color photographic materials, and particularly, to a processing method which is capable of carrying out desilvering sufficiently in a short period of time without any loss of photographic properties.
2. Description of the Prior Art
Generally, a basic process of processing color photographic materials consists of a color developing step and a desilvering step. In the color developing step, exposed silver halide is reduced by a color developing agent to yield silver ard, at the same time, the color developing agent reacts with a color forming agent (a coupler) to produce a dye image. In the subsequent desilvering step, the silver produced in the color developing step is oxidized by an oxidizing agent called a bleaching agent and, then, is dissolved by a complexing agent for silver ion called a fixing agent. By passing through the desilvering step, only the dye image is formed on the color photographic materials.
The above desilvering step is conducted by two baths, i.e., a bleaching bath containing a bleaching agent and a fixing bath containing a fixing agent, by a single bath of a bleach-fixing solution containing both a bleaching agent and a fixing agent, or by using a bleaching bath and a bleach-fixing bath.
Generally, ferricyanide, bichromate, ferric chloride, ferric aminopolycarboxylate complex and persulfate are known as a bleaching agent.
Ferric aminopolycarboxylate complex, particularly ferric ethylendiaminetetraacetate complex has only a little pollution problem unlike ferricyanide and bichromate and has no problem in storage unlike persulfate and, accordingly, is the most generally used bleaching agent. However, the bleaching ability of ferric aminopolycarboxylate complex is not always sufficient. It may attain the envisaged purpose when low speed silver halide photographic materials which mainly use a silver chlorobromide emulsion is subjected to a bleaching or bleach-fixing process. However, when high speed color photographic materials which mainly use a silver chlorobromoiodide or iodobromide emulsion and is color sensitized, particularly color reversal photographic materials used for photofinishing using an emulsion of a high silver content or color negative photographic materials used for photofinishing, are processed, disadvantages such as insufficient desilvering and long bleaching time arise.
On the other hand, West German Patent No. 866,605 specification discloses the use of a bleach-fixing solution containing ferric aminopolycarboxylate complex and thiosulfate as a method for accelerating the desilvering step. However, when the ferric aminopolycarboxylate complex having a weak oxidation ability (bleaching ability) is mixed with the thiosulfate having reduction ability, its bleaching ability is extremely decreased, and it is very difficult to sufficiently desilver high speed color light-sensitive materials for photofinishing of a high silver content and therefore this bleaching solution is impossible to be put into practical use.
Furthermore, a method has been proposed in which two or more bleach-fixing baths are used. For example, Japanese Patent Publication (unexamined) No. 11131/1974 (OLS-2217570) describes a method of processing in a continuous bleach-fixing bath comprising two or more baths to which a regenerated solution for bleach-fixing is supplied by a counter-current method. This method is capable of reducing the amount of waste solution generated from a bleach-fixing solution, but it has the problem that desilvering is not sufficiently carried out, particularly when color photographic materials containing a high content of iodine are processed, because the generated solution contains a high concentration of halogen ions eluted from the color photographic materials, as compared with that of a normal replenishing solution. Furthermore, Japanese Patent Publication (unexamined) No. 105148/1983 describes a method of improving the desilvering property in which at least two bleach-fixing baths are provided, and a fixing component is mainly supplied to the bleach-fixing bath which is near the color developing bath while a bleaching component is mainly supplied to the bleach-fixing bath which is near the water washing bath so as to effect the processing by a counter-current method. However, it is particularly difficult to sufficiently desilver the photographic materials for photofinishing by this method because the oxidation-reduction potential of the first bath is lower than that of the second bath.
Meanwhile, there have been proposed methods for increasing bleaching ability by incorporating various bleach accelerators into a bleaching bath, a bleach-fixing bath or a preceding bath thereof. Such bleach accelerators include mercapto compounds as described in U.S. Pat. No. 3,893,858, British Patent No. 1,138,841 and Japanese Patent Publication (unexamined) 141623/1978, compounds having a disulfide bond as described in Japanese Patent Publication (unexamined) No. 95630/1978, thiazolidine derivatives as described in Japanese Patent Publication No. 9854/1978, isothiourea derivatives as described in Japanese Patent Publication (unexamined) No. 94927/1978, thiourea derivatives as described in Japanese Patent Publications Nos. 8506/1970 and 26586/1974, thioamide compounds as described in Japanese Patent Publication (unexamined) No. 42349/1974, and dithiocarbamates as described in Japanese Patent Publication (unexamined) No. 26506/1980.